A planar inverted F antenna is a modified microstrip antenna having a shape of inverted F.
FIG. 1 is a diagram illustrating a conventional planar inverted F antenna in accordance with a prior art.
Referring to FIG. 1, the conventional planar inverted F antenna includes a rectangular radiation patch 101, a shorting plate 103, a feeding line 105 and a ground plane 107.
The shorting plate 103 is attached between the ground plane 107 and the rectangular radiation patch 101. The feeding line 105 supplies electric power to the rectangular radiation patch 101.
The planar inverted F antenna has been widely used in a wireless communication field since its advantages such as simple structure, easy to manufacture and low cost.
However, the conventional planar inverted F antenna has narrow frequency bandwidth such as 8%˜10% frequency bandwidth of a linear antenna or dipole antenna.
For overcoming the narrow frequency bandwidth, Kathleen L. Virga and Yahya Rahmat-Smaii introduces a new technology in “Low-Profile Enhanced-Bandwidth PIFA antennas for wireless communications packaging” IEEE Transaction on Microwave Theory and Techniques, Vol, 45, No. 10, pp. 1879˜1888, October 1997.
For widening the frequency bandwidth, Kathleen and Yahya implements additional patches to an antenna or two patches connected by tuning diode as a radiation device. As a result, a frequency bandwidth is getting wider, e.g., 14% of bandwidth is increased than the linear antenna or dipole antenna.
However, the antenna introduced by Kathleen and Yahya is complicated and a manufacturing cost is increased.
Beside of the above mentioned antenna, other techniques for overcoming narrow bandwidth of the conventional planar inverted F antenna have been disposed. As mentioned above, in the prior art, wider bandwidth is archived by punching the patch with a slot, providing a double resonating method, attaching a resistor in the shorting plate or providing a multiple structure by loading high dielectric in the patch and ground plate and in between patches. AS a result, the bandwidth of the conventional planar inverted F antenna has become widened, however, it is getting more complicated and for designing the conventional planar inverted F antenna.
In a meantime, an external shape of the radiation patch in accordance with a prior art is limited as a shape of rectangle therefore, it limits to design of structure design of antenna.